The present invention relates to a display device and a source driver. In particular, the present invention relates to a display device suitable for performing an offset cancelling of an amplifier element disposed in each driver regardless of a scanning direction, and to a source driver disposed in the display device.
In a conventional liquid crystal display device, a source driver and a gate driver are provided for driving TFTs (Thin Film Transistor) of a liquid crystal panel. In general, a property of the source driver and the gate driver tends to be affected by an offset voltage of an amplifier element disposed in the source driver and the gate driver. In an extreme case, the offset voltage may cause deterioration of the liquid crystal panel. In a conventional technique (an offset cancelling), in order to minimize the influence of the offset voltage, an offset canceller may be provided for inverting an input polarity of the amplifier element (refer to Patent Reference).
Patent Reference: Japanese Patent Publication No. 2007-264368
The conventional technique for inverting the input polarity includes a dot inversion method, in which the input polarity is inverted per one line, a two line inversion method, in which the input polarity is inverted per two lines, and a frame inversion method, in which the input polarity is inverted per frame. FIG. 12 is a timing chart showing an example of a signal processing operation of a driver driving control circuit of the conventional liquid crystal display device.
As shown in FIG. 12, in each of the dot inversion method, the two line inversion method, and the frame inversion method, it is configured such that the input polarity of the first line is inverted per frame. In order to invert the input polarity of the first line per frame, it is necessary to generate a POL signal and a strove signal (referred to as a STV signal). The POL signal is generated for selecting the polarity of each line between positive and negative. The strove signal is generated for identifying a start point of the frame.
If the STV signal is not input properly, the input polarity is not correctly inverted at the start point of the frame. As a result, it is difficult to properly perform the offset cancelling, so that the desired polarity is not obtained for each line. Accordingly, when the STV signal is not input properly, it is difficult to properly display on the conventional liquid crystal display unit.
In the conventional liquid crystal display device, it is desired that the gate driver is configured to be capable of switching in a scanning direction (a up and down scanning direction), and the source driver is configured to be capable of switching a driving direction (a left and right scanning direction).
If the conventional liquid crystal display device is configured such that the control direction is not switched between the scanning direction and the driving direction, the liquid display panel of the conventional liquid crystal display device may be designed according to a predefined driving direction. Accordingly, it is possible to design the gate driver and the source driver accordingly. In this case, it is possible to shear the STV signal for the gate driver and the source driver.
On the other hand, when the conventional liquid crystal display device is configured such that the control direction is switched between the scanning direction and the driving direction, as disclosed in Patent Reference, it is necessary to input the STV signal separately to the gate driver and the source driver, so that the start point of the frame is properly defined.
In the conventional liquid crystal display device, when the STV signal is sheared for the gate driver and the source driver, it is difficult to properly switch the scanning direction (the up and down scanning direction) in the gate driver and the driving direction (the left and right scanning direction) in the source driver as explained below with reference to FIGS. 13 to 16.
FIG. 13 is a block diagram showing a driver driving control circuit of the liquid crystal panel disposed in the conventional liquid crystal display device upon scanning in a forward scanning direction. FIG. 13 illustrates a transmission path of the STV signal in the forward scanning direction in the driver driving control circuit.
As shown in FIG. 13, the driver driving control circuit includes a liquid crystal panel 71; a timing controller 72; gate drivers 731 to 73n; source drivers 741 to 74m; an STV signal wiring portion 75 for transmitting the STV signal; and an LRb wiring portion 76 for transmitting an LRb signal for defining the left and right scanning direction.
In the driver driving control circuit shown in FIG. 13, the gate drivers 731 to 73n, the source drivers 741 to 74m; and the STV signal wiring portion 75 are arranged such that the STV signal is processed at the start point of the frame. Further, the LRb wiring portion 76 is arranged such that the left and right scanning direction can be selected with the LRb signal for defining the left and right scanning direction.
It should be noted that the forward scanning direction (with a left upper start point of the liquid crystal panel 71) is defined as a direction of scanning from the gate driver 731 to the gate driver 73n and a direction of scanning from the source driver 741 to the source driver 74m, and an reverse scanning direction (with a right lower start point of the liquid crystal panel 71) is defined as an opposite direction to the forward scanning direction.
An operation of the driver driving control circuit shown in FIG. 13 will be explained next. When the scanning is performed in the forward scanning direction, the STV signal output from the timing controller 72 is processed in the order from the gate driver 731 to the gate driver 73n. Further, at the same time when the STV signal is input into the gate driver 731, the STV signal output from the timing controller 72 is input into and processed in the order from the source driver 741 to the source driver 74m. 
FIG. 14 is a timing chart showing the operation of the driver driving control circuit of the liquid crystal panel disposed in the conventional liquid crystal display device upon scanning in the forward scanning direction. In FIG. 14, the STV signal input into the gate driver 731 shown in FIG. 13 is designated with STVb, and the STV signal input into the source drivers 741 to 74m shown in FIG. 13 is designated with STVs.
As shown in FIG. 14, the STV signal is input into the gate driver 731 and the source drivers 741 to 74m at the start point of one frame. Accordingly, it is possible to normally perform the offset cancelling per frame in the gate drivers 731 to 73n and the source drivers 741 to 74m. 
In the conventional liquid crystal display device having the configuration shown in FIG. 13, however, when the liquid crystal panel is configured such that the forward scanning direction is switched to the reverse scanning direction, the STV signal is not input into the source drivers 741 to 74m at the start point of one frame.
FIG. 15 is a block diagram showing the driver driving control circuit of the liquid crystal panel disposed in the conventional liquid crystal display device upon scanning in the reverse scanning direction. FIG. 15 illustrates a transmission path of the STV signal in the reverse scanning direction in the driver driving control circuit.
As shown in FIG. 15, upon scanning in the reverse scanning direction, the STV signal is input into in an order from the gate driver 73n, the gate driver 73n-1, to the gate driver 731. Afterward, the STV signal is input into the source drivers 741 to 74m. 
FIG. 16 is a timing chart showing the operation of the driver driving control circuit of the liquid crystal panel disposed in the conventional liquid crystal display device upon scanning in the reverse scanning direction. In FIG. 16, the STV signal input into the gate driver 73n shown in FIG. 15 is designated with STVd, and the STV signal input into the source drivers 741 to 74m shown in FIG. 15 is designated with STVs.
As shown in FIG. 16, the STV signal STVd is input at a timing different from that of the STV signal STVs. More specifically, the STV signal STVs is input at an end point of one frame.
As described above, it is necessary to input the STV signal at the start point of the frame for properly performing the offset cancelling. When the STV signal is input at the end point of the frame, it is difficult to obtain the desired polarity, thereby deteriorating the liquid crystal panel.
In the conventional liquid crystal display device, the STV signal wiring portion is sheared between the gate drivers and the source drivers. Accordingly, when the control direction of the scanning direction and the driving direction is switched in the liquid crystal panel, the STV signal is not processed at the start point of the frame, and is processed at the end point of the frame. Accordingly, it is difficult to obtain the desired polarity, thereby deteriorating the liquid crystal panel. It appears difficult to solve the problems in the conventional liquid crystal display device.
In view of the problems of the conventional liquid crystal display device described above, an object of the present invention is to provide a display device capable of solving the problems of the conventional liquid crystal display device. In the present invention, it is possible to switch the control direction of scanning of a liquid crystal panel after the liquid crystal panel is designed while a STV signal wiring portion is sheared between gate drivers and source drivers.
Further objects and advantages of the invention will be apparent from the following description of the invention.